This invention relates to sewing machine needles, and more particularly to sewing machine needles which have flats on both sides of the needle in the area of the needle eye. These flats taper down towards the needle point.
The needles that have been heretofore available for use in straight needle industrial sewing machines, and particularly for Class 39800 overedge sewing machines, manufactured by Union Special Corporation, suffer from certain drawbacks. The manner in which the needles are formed is one of these drawbacks. Such overedge sewing machine needles are provided with longitudinally extending grooves, either on the front or backside of the needle, or on both sides, and serve to protect the thread as it passes through the fabric. Heretofore these grooves have been produced on the needle by using a milling cutter thereby physically removing the metal.
It was likewise the practice to produce the needle eye in a similar manner. Most needle manufacturers have since changed the method of producing the eyes and grooves upon the needle. Rather than milling the thread groove and needle eye into the sewing machine needle they are now produced by striking the needle with dies. Eyes and grooves manufactured by such a process are usually termed either "struck" or "die press" groove and eye needles or some close variation of these terms. By utilizing this stamping process the metal is compressed causing it to relocate and form the needle. This method also adds strength to the needle.
The stamping of the needle eye does prove to have its disadvantage in that it can result in certain imbalances, particularly in the needle eye area. Such imbalances during high speed operation of the sewing machine can result in the needle either vibrating or fluttering. This erratic movement of the needle can cause the point, for example, to strike the machine throat plate, the top of the looper, or the needle guards, thereby causing needle breakage resulting in costly downtime. The degree of uncertainty caused by this stamping process and by the displacement or relocation of the metal forming the needle also creates a certain amount of uncertainty with regard to the proper stitch formation. That is, in order to produce good stitch formation it is desirable that the looper and spreader get as close to the needle as possible thereby lessening the chances of skipped stitches. Skipped stitches are caused, for example, with synthetic thread because it clings to the fabric and the needle rather than forming a loop which is grasped by either the looper or the spreader. As is apparent, if an uncertainty exists as to the shape of the needle it may be necessary to make adjustments on the looper and spreader for each and every needle change, a situation which is very undesirable and costly. Another drawback with having the grooves and needle eyes stamped on the needle is the fact that the top edges of certain elements subsequent to stamping may be very sharp. This would cause both fabric cutting and increases the possibility of operator injury.
Another problem associated generally with needles which are employed with sewing machines is that of needle heat. That is, as the needle passes into and out of the fabric workpiece, frictional heat is generated. In order to overcome this difficulty, it has been suggested that a ball eye needle be employed in certain particular sewing functions. One of the main advantages in using a ball eye needle is that the needle eye is larger at the needle eye area than the blade portion above it, thereby mitigating the heat built up on the blade portion by reducing its contact with the fabric.
In view of the foregoing, the present invention has for an object to provide a needle having stamped grooves and a stamped needle eye which is substantially uniform in the area of the needle eye.
It is another object of this invention to provide a needle having both stamped grooves and a stamped eye but yet does not leave the top edges of the flat surface provided thereon sharp.
Yet another object of this invention is to provide a stamped ball eye needle having two stamped grooves and provided with flats in the area of the ball eye thereby decreasing the size thereof and decreasing the amount of needle heat produced during the sewing operation.
Still another object of this invention is to provide a stamped sewing machine needle which is thereafter so modified as to allow a closer approach of the looper and the spreader to the needle thereby assuring better stitch formation.
Yet another object of this invention is to provide a stamped sewing machine needle having flats thereon which allows for greater amount of clearance between the looper or spreader when large diameter needles are utilized thereby lessening needle breakage.
According to the invention, the improved needle comprises a leading end portion of generally conical shape, an eye portion, a shank portion which is at the butt or trailing end of the needle, and a blade portion intermediate the butt portion and the eye portion. In the preferred embodiment, the blade portion has grooves along the top and bottom side thereof. These grooves as well as the needle eye are stamped or struck with a die as described above. On the groove sides of the needle, beginning at an area adjacent the blade portion and extending toward the conically shaped end portion, are tapered flats. These tapered flats are created by the physical removal of material and slope or taper downwardly toward the leading end or point end of the needle.
With the foregoing objects, aims and advantages of the invention in view, the preferred embodiment and the manner of use will now be set forth in the following detailed description, the appended claims, and in the several views illustrated in the accompanying drawings.